Device for controlling the ignition in an internal combustion engine

ABSTRACT

The device for controlling the ignition in an internal combustion engine comprises a circuit controlled by an electromagnetic switch coupled with the rotation of the motor and connected to the ignition coil thereof, said magnetic switch having a maintenance circuit altering the opening of the switch in dependency of the speed of the engine.

United States Patent lnventor Appl. No. Filed Patented Assignee PriorityBernard Varaut Draveil, France 799,416

Feb. 14, 1969 Jan. 19, 1971 Compagnie Des Compteurs Paris, France acompany of France Feb. 27, 1968 France DEVICE FOR CONTROLLING THEIGNITION IN AN INTERNAL COMBUSTION ENGINE 3 Claims, 3 Drawing Figs.

US. Cl

[51] Int. Cl F02p 5/08 [50] FieldofSearch 123/148E,148M,117.1;315/209,219

[56] References Cited UNITED STATES PATENTS 3,308,341 3/1967 McLaughlin315/219 3,356,896 12/1967 Shano H 315/209 3,433,208 3/1969 Dogadko et a1123/148E Primary ExaminerLaurence M. Goodridge AttorneyPierce, Scheffler& Parker ABSTRACT: The device for controlling the ignition in aninternal combustion engine comprises a circuit controlled by anelectromagnetic switch coupled with the rotation of the motor andconnected to the ignition coil thereof, said magnetic switch having amaintenance circuit altering the opening of the switch in dependency ofthe speed of the engine.

The present invention relates to an ignition device for the advance ofwhich is controlled by an electromagnetic type of detector.

It is known to use a disc or magnetic pole cam for actuating a reedswitch in an internal combustion engine.

By its operational principle, this kind of switch introduces an ignitiontime lag which is usually corrected by artificial mechanical means thatare often complicated so as to obtain an ignition correctionsatisfactory at very high speeds. The main object of the presentinvention is to produce an improved device that will prevent thesedisadvantages by acting directly on the response of the switch.

' The device according to the invention is essentially characterized inthat it comprises an excitation circuit for the ignition coil controlledby an electromagnetic type detector by the opening of a switch coupledto the rotation of the crankshaft cam, and a maintenance circuitsubjected to a voltage inversely proportional to the speed and retardingthe opening of the switch for altering the ignition.

According to an embodiment of the invention, the energizing circuitcomprises a flexible reed electromechanical relay, of the dry reedswitch" type, for instance, setting up the control current of theignition coil.

According to a development of the invention, the maintenance circuitcomprises a frequency-to-voltage converter, producing a voltageinversely proportional to the speed, said converter being controlled bythe switch and the voltage being applied to a maintenance winding ofsaid electromechanical relay.

Other, characteristics of the invention will moreover be revealed by thedescription which follows, as well as the accompanying drawings, givenby way of nonrestrictive example.

FIG. 1 is a partial perspective of an internal combustion enginecomprising the device of the invention.

FIG. 2 is a diagram of the ignition device and advance static correctionaccording to the invention.

FIG. 3 is a diagram of the curves of the ignition advance according tothe invention.

FIG. 1 shows diagrammatically a four cylinder engine 1 of which only onecylinder has been illustrated. In each cylinder a piston2 slides whoseconnecting-rod 3 is jointed at its foot to one of the crank pins 4 ofthe crankshaft 5 rigidly connected to a flywheel 6 carrying a disc 101and also to a distributing device 7 which is intended to direct in agiven order the current pulses produced from the device of theinvention, designated on the whole by reference numeral 8, to each sparkplug 9. The device 8 is, in this example, connected to a switch 102forming part of it a and which is intended to detect the successivepassage of two magnetic poles 11 and 12 carried by the disc 101. Twocurrent pulses are then produced setting off two sparks by two distinctspark plugs for each revolution of the crankshaft 5, as is the case fora four-cylinder engine operating according to a four-stroke cycle.

In FIG. 2, the disc 101 comprises marked or projecting magnetic poleswhose number is in direct relation to the number of cylinders andcycles. The disc 101 controls a magnetic switch reed relay type 102 withcontacts 103, 104 so that at each passage of a pole in front of thecontact, said contact is closed.

The switch 102 is connected between i a positive line 105 and a negativeline to the earth 108 by means of a resistor 107. A resistor 109connects the point 106, common to the resistor 107 and the switch 102,to the base of a transistor 110. Said transistor has its emitter earthedin 108 and its collector connected to the positive line 105 by means ofthe primary 111 a, of an ignition coil 111, and a diode 114 in series.

The circuit, comprising the positive line 105 and passing through theswitch 102, the resistor 109, the base and emitter of the transistor110, and closed by the diode 114 and primary winding 111a, representsthe excitation circuit of the ignition coil 111 whose coil 111 b formshigh voltage output connected to the plugs, for example spark plug 9 ofFIG. 1.

Between the point 106 and earth 1108 a frequency-to-voltage converter112 is connected suppllying a voltage inversely proportional to thefrequency of the signal it receives from the point 106. This voltage isapplied by a conductor to the terminals of the maintenance winding 113of the switch 102, the voltage being so much the higher as the frequencyof the input signal is lower, hence that the speed N of the engine islower according to the relation:

FIG. 3 gives the variation curve of said voltage: V f (N).

As shown in FIG. 2, the converter device 112 comprises a capacitor C anda resistor R mounted in paralleled between the conductor of the earth Mand the conductor 100 below a diode D and thus forming the maintenancecircuit of the excitation circuit.

When the switch 102 is subjected to a magnetic pole of the disc 101, thecontacts 103, 104 are closed.

A positive potential is then applied by means of the resistor 109 to thebase of the transistor 110 which is saturated and becomes conductivethus supplying the primary winding 111 a ofthe ignition coil 111.

At the moment when the crankshaft approaches top dead center the disc101 has revolved and no longer subjects the switch 102 to the influenceof a magnetic pole. The contacts 103, 104 open and as there is nocurrent circulating in the base of the transistor 110, said transistoris blocked. The primary 1 11a of the coil 111 is no longer supplied andthe breaking of the circuit received on the winding lllb acts forcausing a spark.

The working of the switch 102 described in the foregoing, corresponds toa maximal advance of the ignition.

The converter 112 receives a signal from the point 106, every time theswitch 102 closes, that is to say, at the moment when a pole of the disccomes in front of the contact. The converter is provided for deliveringa voltage V F (N) inversely proportional to the speed of the disc 101(curve 201, FIG. 3). This voltage V is applied to the winding 113 of theswitch 102 and whose magnetic field opposes that produced by the polefacing disc 101.

At low speeds, the voltage V (curve 201, FIG. 3) is sufficientlyimportant to cause the winding 113 to produce a magnetic field whichdelays the opening of the switch 102 during the passage of the poles ofthe disc 101, opening which does not occur at this moment. In thatwhich. follows, the angle a of ignition advance is the angle existing atthe moment when the spark is produced between the portion of one of thecrankpins of the crankshaft and that which it occupies when the pistonto which it is connected is at its top dead center corresponding to theend of the compression stroke of the fuel mixture contained in thecylinder.

In FIG. 3, the curve 202 shows the variation of the angle of advance aas a function of the number N of revolutions of the engine. One seesthat the origin (N 0) of the curve 202 corresponds to the maximalvoltage V and to a minimal advance.

When the rotation speed of the crankshaft increases, voltage decreases(curve 201, FIG. 3) and, hence the magnetic field of the winding 113,diminishes to the same extent, which delays the opening of the switch102 by as much.

For a maximum speed, the direct action of the poles of the disc 101become preponderating; the opening of the contacts 103, 104, andconsequently, the operating of the energizing circuit happens at thegiven moment settled for a maximum fixed advance (end of the curve 202,FIG. 3).

It is quite obvious that the intermediate points of the advance curve(202, FIG. 2) result from the difference between the antagonist magneticfields produced by the winding 113 and the poles of the disc 101.

Without going outside the scope of the invention, the shape of the disc101 and magnetic poles that it comprises can be modified for varying theadvance correction.

I claim:

I. An ignition system for an internal combustion engine, comprising incombination a magnetic switch fitted with a maintenance coil, rotarymagnetic member located in relationship with said magnetic switch foroperation thereof, means coupling said magnetic member to the internalcombustion engine for rotating said member in synchronism with therotation speed of the engine so that said magnetic switch producessignals whose frequency depends on said speed, an electronic gateconnected both to the magnetic switch and to said maintenance coil, afrequency to-voltage converter also connected both to the magneticswitch and to the maintenance coil and providing a voltage so that theproduct of the voltage by the frequency of the signal coming from themagnetic switch is a linear function of said frequency, whereby avoltage is applied to the maintenance coil to delay the operation of theswitch and then of the gate in dependency of the speed of the engine,and an ignition coil connected on the one hand to one spark plug of saidengine and, one the other hand, to said gate whereby a spark is producedin said spark plug at the moment when said gate is open, this momentbeing delay in dependency ofthe rotation speed of the engine.

2. An ignition system as set forth in claim 1, in which the converterfrequency-to-voltage device comprises a capacitor and resistor circuitparallely mounted between the maintenance coil and earth and a diodeconnected between said circuit and the gate. I ,1

3. A device according to claim 1 in which the magnetic switch is ofa dryreed relay.

1. An ignition system for an internal combustion engine, comprising incombination a magnetic switch fitted with a maintenance coil, rotarymagnetic member located in relationship with said magnetic switch foroperation thereof, means coupling said magnetic member to the internalcombustion engine for rotating said member in synchronism with therotation speed of the engine so that said magnetic switch producessignals whose frequency depends on said speed, an electronic gateconnected both to the magnetic switch and to said maintenance coil, afrequency to-voltage converter also connected both to the magneticswitch and to the maintenance coil and providing a voltage so that theproduct of the voltage by the frequency of the signal coming from themagnetic switch is a linear function of said frequency, whereby avoltage is applied to the maintenance coil to delay the operation of theswitch and then of the gate in dependency of the speed of the engine,and an ignition coil connected on the one hand to one spark plug of saidengine and, one the other hand, to said gate whereby a spark is producedin said spark plug at the moment when said gate is open, this momentbeing delay in dependency of the rotation speed of the engine.
 2. Anignition system as set forth in claim 1, in which the converterfrequency-to-voltage device comprises a capacitor and resistor circuitparallely mounted between the maintenance coil and earth and a diodeconnected between said circuit and the gate.
 3. A device according toclaim 1 in which the magnetic switch is of a dry reed relay.